Dialysis Machine Flashcards
What is the function of the kidneys ?
Maintenance of electrolyte balance
Fluid balance
Why do kidneys fail ?
Bacterial or Viral Infections
Genetic Disorders
sustained High blood pressure
Diabetes
How long does a patient need to undergo dialysis for per week and how much blood is filtered per week via dialysis ?
3 times per week for between 4 to 5 hours.
Roughly 150-200 litres of blood are filtered per session.
What scientific principles underpin a dialysis machines function ?
Diffusion
Reverse osmosis
Ultrafiltration
Convection
What are the features of the blood circuit of a dialysis machine ?
May require the creation of a fistula for the flow of blood ( combination of a vein and artery via surgery).
An air trap to remove bubbles from returning blood.
A dialyser to filter out excess and allow supply of necessary electrolytes.
Pressure monitors before entry, before the dialyser and before the air trap.
A pump to increase pressure / speed of blood.
Anticoagulant to retain the liquid flow of blood
Why do we use a dialyser ?
A dialyser helps to supply the right balance of electrolytes to the blood by using dialysate fluid with specific quantities to induce diffusion through its hollow fibres in the necessary direction.
What are the properties of dialysate fluid ?
Requires pure “Ro” water to be most effective. Contains bicarb as part of sodium intake but more so as a buffer for smoother dialysis.
How is water quality measured ?
Using a quantity known as conductivity (Siemens) which is the inverse of resistance. Ro water must be less than 10 micro siemens .
How does reverse osmosis work ?
applies a high pressure and forces pure water molecules under pressure to move to the opposite side. Done to increase the purity of water through a semi-permeable membrane.
What are the features of the non - blood side of the circuit ?
Water is deaerated and regulated for pressure.
It will contain a blood leak detector after the dialyser (infrared ).
Water is heated to an appropriate temperature so the blood returns to the body between 35 and 42 degrees.
What can ultrafiltration do for a dialysis patient ?
It can remove excess weight for the patient and the principle is also used in the dialyser and factored into the calculations.
What safety systems are present in a dialysis machine ?
Temperature sensors and alarms.
Conductivity limits and alarms.
The machine has bypass valves and tube locks for the case of emergency but will return all blood before locking tubes.
Ultrafiltration detection and pressure alarms and sensing.
